The invention relates to a piston compressor, particularly a hermetically enclosed refrigerant compressor, with a crankshaft, which is supported in an axial bearing in relation to a bearing housing, and with an oil pump arrangement.
A piston compressor of this kind is known from U.S. Pat. No. 3,451,615. An oil pump arrangement working by means of centrifugal force is arranged at the lower end of the crankshaft, the oil pump arrangement immersing in an oil sump and supplying oil through the crankshaft to a bearing housing, in which the crankshaft is radially and axially supported. In the area of the radial bearing, the crankshaft has a spirally extending lubricating groove, through which the oil from the oil pump arrangement is supplied. Axially above the bearing housing, the crankshaft has a radially projecting flange, which is supported on the bearing housing, and forms an axial bearing together with the bearing housing. The lubricating groove extends up to this area, so that, for lubricating purposes, oil supplied through the lubricating groove also reaches the area of the axial bearing.
A similar embodiment is known from DK 164 828 B. Also here the crankshaft has a spirally extending groove on its surface, with which it is supported in a bearing housing.
In the area of the axial bearing, oil from the end of the lubricating groove, which rotates with the crankshaft, reaches the radial inner area of the axial bearing, from where it must spread axially outwards. However, it is not always ensured that sufficient oil reaches the axial bearing to be spread over the complete bearing surface. Occasionally, radially extending channels have been provided in the axial bearing, which should ensure an improved transport of the oil radially outwards. However, such a channel or such channels also cause that near these channels the oil layer has only a limited load-bearing capability. This requires the use of a lubricating oil with a relatively high viscosity. This again causes an increased energy consumption.
The invention is based on the task of improving the lubricating properties.
With a piston compressor as mentioned in the introduction, this task is solved in that in the axial bearing between the crankshaft and the bearing housing an oil distribution channel extending in the circumferential direction is arranged, a control arrangement being arranged between the oil pump arrangement and the oil distribution channel, which control arrangement connects the oil pump arrangement with the oil distribution channel for a predetermined, short period, at least once during each rotation of the crankshaft.
With this embodiment it is ensured that the oil can be supplied into the oil distribution channel with a higher pressure. This higher pressure is, among other things, generated in that the oil cannot flow permanently into the oil distribution channel, but only when the control arrangement releases the connection between the oil pump arrangement and the oil distribution channel. Thus, oil pulses occur, which cause a somewhat higher pressure of the oil in the oil distribution channel. This causes an improvement of the support of the crankshaft in the bearing housing. It also leaves more freedom in connection with the selection of the placing of the oil channel, that is, the oil channel does not have to be arranged in the immediate proximity of the bore, through which the crank shaft is guided. This permits an additional improvement of the oil distribution, as the oil must no longer flow through the total radial extension of the axial bearing, but, for example, can be supplied in a central area, so that it can penetrate radially inwards and outwards. As, through a design measure, it has now been ensured that the lubrication is improved, an oil with a lower viscosity can be used. This oil causes lower losses, so that the efficiency can be improved. With the same pump output, the supplied amount of oil is increased, so that again the oil pressure in the oil distribution channel increases, which again causes better lubricating properties.
Preferably, the control arrangement is controlled by the crankshaft. As the oil pulse must be generated at least once per rotation of the crankshaft, the control by means of the crankshaft provides a certain automation that needs no further monitoring.
It is also preferred that the oil pump arrangement is connected with at least one lubricating groove on the circumference of the crankshaft, which groove overlaps the opening of an oil supply channel on a rotation of the crankshaft, the other end of the oil supply channel opening into the oil distribution channel. The lubricating groove is known per se. Together with the opening of the oil supply channel, it forms the control arrangement, which ensures that on each rotation a connection from the oil pump arrangement to the oil distribution channel can be established at least once. This connection occurs, when, on a rotation of the crankshaft, the spirally extending lubricating groove (or grooves) overlap the opening of the oil supply channel. When this overlapping is not established, the opening is covered by the circumferential surface of the crankshaft, so that the oil from the oil distribution channel cannot flow back, but is used completely for the lubrication of the axial bearing. The fact that the supply of the oil distribution channel per rotation only takes a short time, the remaining time can be spent on building up a higher pressure in the lubricating groove. When the lubricating groove overlaps the opening of the oil supply channel, this higher pressure will be passed on to the oil distribution channel.
Preferably, the lubricating groove ends at a predetermined distance before the axial bearing, and the opening of the oil supply channel overlaps the end of the lubricating groove. This ensures a relatively exact definition of the allocation between the lubricating groove and the opening of the oil supply channel. At the end of the oil supply channel an oil backup may be generated, which again leads to a pressure increase, which can propagate through the oil supply channel into the oil distribution channel.
Preferably, the end of the lubricating groove is provided with an inclined wall. On a rotation of the crankshaft, this inclined wall pushes the oil ahead of itself and thus generates a pressure component radially outwards. When this inclined wall is led past the opening of the oil supply channel, it presses the oil further into the oil supply channel, which causes an additional pressure increase in the oil supply channel. That is, the inclined wall increases the amplitude of the oil pulse.
Preferably, an oil pocket is formed at the end of the lubricating groove. The oil pocket is somewhat extended in the axial direction. Thus, a larger oil supply is available, which can be pumped into the oil distribution channel over a longer period.
Preferably, the oil supply channel is inclined in relation to the rotational axis of the crankshaft. Thus, the oil distribution channel can be arranged radially further outwards.
Preferably, the oil distribution channel is divided into several sections in the circumferential direction, each section being supplied separately. This increases the number of oil pulses per rotation of the crankshaft. This leads to an increase of the amount of oil pumped into the axial bearing per rotation of the crankshaft. As the individual sections of the oil distribution channel are smaller, that is, have a smaller volume, this leads to an additional pressure increase of the oil in the axial bearing.
In this connection, it is preferred that each section has an oil supply channel. This oil supply channel of each section will then overlap the lubricating groove on the circumference of the crankshaft exactly once per rotation of the crankshaft. This is a relatively simple opportunity of establishing a control arrangement for each section of the oil distribution channel.